1. Field of the Invention
Embodiments of the present invention generally relate to a method of dynamically controlling the temperature of a solar cell substrate during microcrystalline silicon deposition.
2. Description of the Related Art
Photovoltaic devices (PV) or solar cells are devices that convert sunlight into direct current (DC) electrical power. PV or solar cells may be single junction or multi-junction with each junction having a p-doped region, an intrinsic region, and an n-doped region to form a p-i-n structure. The intrinsic region may be formed by amorphous silicon, but amorphous silicon does not utilize as wide a spectrum of sunlight as microcrystalline silicon.
Microcrystalline silicon, on the other hand, while utilizing a wider spectrum of sunlight as compared to amorphous silicon, has a much lower absorption coefficient than amorphous silicon and therefore does not deposit at as fast as amorphous silicon. The deposition rate of microcrystalline silicon can be increased by increasing the power density, but a higher power density usually leads to a higher processing temperature. Higher processing temperatures may not be beneficial because the dopant in adjacent layers may diffuse into other layers and damage the solar cell.
Because of microcrystalline silicon's ability to use a wider spectrum of sunlight, it would be beneficial if microcrystalline silicon could be deposited at a faster rate without risk of damaging the solar cell. Therefore, there is a need in the art for a method of depositing microcrystalline silicon at a faster rate without damaging the solar cell.